Simultaneous determination of seven anthraquinones in rat plasma by Ultra High Performance Liquid Chromatography–tandem Mass Spectrometry and pharmacokinetic study after oral administration of Semen Cassiae extract

Ethnopharmacological relevanceSemen Cassiae, called Juemingzi in China, is the seed of the annual Cassia obtusifolia L., of the leguminosae family. It has been used as healthy drinks to alleviate constipation and improve eyesight for many years in China.Aim of the studyA simple sensitive UHPLC–MS/MS method has been developed and validated for the simultaneous determination and pharmacokinetic study of chrysophanol, emodin, aloe-emodin, rhein, physcion, obtusifolin and aurantio-obtusin in rat plasma.Materials and methodsChromatographic separation was accomplished on a C18 column with a 5 min gradient elution. A tandem mass spectrometric detection was conducted using multiple reaction monitoring (MRM) via an electrospray ionization (ESI) source and operating in the negative ionization mode. The samples were prepared by LLE with ethyl acetate after being spiked with an internal standard (butylparaben).ResultsThe current UHPLC–MS/MS assay was validated for linearity, intra-day and inter-day precisions, accuracy, extraction recovery and stability. The method was linear for all analytes over investigated range with all correlation coefficients greater than 0.9900. The lower limit of quantification (LLOQ) of each analyte was lower than 5 ng/mL. Intra-day and inter-day precisions were less than 14.99%. The relative errors of accuracies were in the range of −14.60% to 5.11%. The mean recoveries and matrix effects of anthraquinones were higher than 65.54% and 93.26%, respectively. After oral administration 1.25 g/kg of Semen Cassiae extract, the maximum plasma concentration (Cmax) was 1189.25±333.40 ng/mL for chrysophanol, 38.48±3.15 ng/mL for emodin, 79.20±34.76 ng/mL for aloe-emodin, 152.70±23.91 ng/mL for rhein, 461.85±266.77 ng/mL for physcion, 243.59±22.71 ng/mL for obtusifolin and 1950.44±638.86 ng/mL for aurantio-obtusin, respectively. The time to reach the maximum plasma concentration (Tmax) was 0.333±0.071 h for chrysophanol, 0.333±0.059 h for emodin, 0.333±0.009 h for aloe-emodin, 0.333±0.09 h for rhein, 0.167±0.002 h for physcion, 0.5±0.074 h for obtusifolin and 0.333±0.06 h for aurantio-obtusin, respectively.ConclusionThe proposed method was further applied to investigate the pharmacokinetics of seven anthraquinones after oral administration of Semen Cassia extract to rats.